The validity of canine platelet aggregometry in predicting vascular graft patency.
 Several laboratories have found canine platelet aggregometry predictive of thrombotic potential in vascular grafts.
 Adenosine diphosphate (ADP) is a frequently used agonist, often at unspecified or differing concentrations.
 This study was designed to evaluate the predictive value of ADP-induced platelet aggregometry and the validity of the methodology.
 Platelet aggregometry in response to 2 x 10(-5) M ADP was assayed in 70 dogs.
 Twenty-six percent were aggregators, 51% were non-aggregators, and 20% were indeterminant.
 All dogs were then treated with aspirin and dipyridamole.
 Vascular prostheses were implanted bilaterally (aorto-iliac) and anti-platelet therapy continued for two weeks.
 Dose-response to ADP was studied at three concentrations in 20 dogs.
 At 2 x 10(-5) 1/20 aggregated, at 4 x 10(-5) 3/19 aggregated and at 2 x 10(-4) 15/20 aggregated.
 Time between samples and study was evaluated in 11 dogs, with 2/11 changing from non-aggregator to aggregator at two or three hours.
 Daily reproducibility was studied in 70 dogs, 14 of which changed aggregation status between days.
 Patency was 58/68 (85%) for non-aggregators, 23/34 (68%) for aggregators (p = 0.038).
 Platelet aggregometry has significant predictive value for graft patency but methodology must be specified and standardized.
